1. Field of the Invention
The present invention relates to a separator for a molten carbonate fuel cell, and, more particularly, to a separator for a molten carbonate fuel cell, which can decrease the volume of the fuel cell compared to conventional fuel cells because the separator is provided therein with a fuel gas reforming channel, and which can reduce production costs because the separator has a simple structure.
2. Description of the Related Art
Generally, a fuel cell is a generator serving to convert chemical energy into electrical energy through the oxidation and reduction of reactants. Unlike other existing types of chemical energy, the fuel cell causes hardly any pollution or noise because it discharges only water (H2O) as a by-product, and the chemical reaction in the fuel cell is simple. Therefore, the fuel cell is receiving great attention as an alternative energy source for the next generation.
In particular, among fuel cells, a molten carbonate fuel cell (MCFC) uses molten carbonates as an electrolyte and operates at about 650° C., and thus the electrochemical reaction rate in the MCFC is rapid. Therefore, the molten carbonate fuel cell does not need a precious metal catalyst, such as a platinum catalyst, and can exhibit high thermal efficiency of 60% or more when it is used together with electricity and high temperature, and thus it can be used for combined heat and power generation using the gasification of coal.
A unit cell of a molten carbonate fuel cell includes an anode and a cathode, in which an electrochemical reaction is conducted, a separator for forming a fuel gas channel and an oxidant gas channel, a charge collecting plate, an electrolyte plate fabricated in the form of a sheet to meet the convenience of stacking, and a matrix for storing molten carbonate. In the unit cell of the molten carbonate fuel cell, when fuel gas is supplied to an anode and oxidant gas is supplied to a cathode, an electrochemical reaction is conducted in each of the electrodes, thus obtaining direct current voltage.
Since the voltage obtained from the unit cell is about 0.7˜1.2 V, which is low, at the time of rated electric discharge, in practice, a plurality of unit cells is layered, so that the total voltage of the fuel cell is increased and the total surface area of the unit cells is also increased, thereby obtaining high power. The structure in which a plurality of unit cells is layered is referred to as “a stack”.
Since such a stack determines the power generation efficiency, lifespan and performance of the molten carbonate fuel cell, the shape of a separator constituting the stack and the method of supplying fuel into the separator are very important.
Meanwhile, in the molten carbonate fuel cell, since a water vapor reforming reaction for forming a reformed gas containing hydrogen using methane gas and water vapor, which is an endothermic reaction, is conducted together with an electrochemical reaction (anode: oxidation reaction, cathode: reduction reaction), which is an exothermic reaction, a fuel reforming apparatus is used to supply heat generated from the electrochemical reaction to the water vapor reforming reaction, which requires heat.
However, conventional molten carbonate fuel cells are problematic in that the above fuel reforming apparatus is separately provided outside the fuel cell and connected with a separator, and thus the volume thereof is increased and the structure thereof is complicated. Specifically, in conventional molten carbonate fuel cells, fuel gas is reformed from the fuel reforming apparatus provided outside the fuel cell, and then the reformed fuel gas is supplied into a stack through a separator connected with the fuel reforming apparatus. For this reason, the conventional molten carbonate fuel cells are problematic in that the volume thereof is increased, and in that the structure for connecting the fuel reforming apparatus with the separator is complicated, so that the installation thereof is not easy, thereby increasing production costs.